This invention relates generally to an osteotomy technique, and more particularly to a method for performing a greatly simplified proximal tibial osteotomy. A preferred manner of practicing the invention is described in conjunction with veterinary surgery on the leg of a dog.
The cranial or anterior cruciate ligament restrains cranial drawer or sliding motion of the tibia of a dog. When the cranial cruciate ligament is disrupted or injured, the tibia moves forward relative to the femur, leading to further injury of the musculature, ligaments or meniscus. A wide variety of methods of repairing the cranial cruciate ligament have been suggested, ranging from collagen ligament implants to synthetic ligament implants. Extra-articular repair devices have also been proposed, but none of these has been very successful. Collagen implants stretch with use, leaving the knee area unstable, while synthetic implants are unable to withstand the varied forces exerted on the knee. Extra-articular repairs decrease mobility, and place undue stress on the soft tissue surrounding the joint which is not designed for constant loads.
It has been recognized that one problem with most techniques for repairing a dog's cranial cruciate ligament is that the phenomenon of cranial tibial thrust has not been appreciated. This phenomenon results in force factors having compressive and cranial or anterior components. The compressive components are satisfactorily absorbed by the tibia, as are the cranial tibial forces when the cranial cruciate ligament is operating satisfactorily. When the cranial cruciate ligament is weakened by injury or is congenitally malformed, cranial tibial thrust can be a problem. Many prior efforts at repair of a weakened cranial cruciate ligament ignore the cranial tibial thrust phenomenon, and have failed to recognize that this phenomenon results in the ligament being placed under stress while healing was intended to occur. Such stress clearly retards or prevents healing.
Once cranial cruciate rupture occurs, so-called cranial drawer or sliding motion, that is, unrestrained cranial motion of the tibia with respect to the femur following such rupture, results in more severe injury to the dog's leg in the form of soft tissue (medial meniscus) impingement. Surgical attempts have been addressed to restraining cranial draw motion but, until recently, no attempt has been made to deal with internally generated cranial tibial thrust.
One technique which has been proposed over the years to deal with these problems is so-called cuneiform osteotomy--that is, surgical removal of a bone wedge to correct impairments to the bone, the musculature or the ligamental support structure associated therewith. For example, I describe such a technique in my now-pending, prior-filed patent application, Ser. No. 570,458, filed Jan. 12, 1984 for "APPARATUS AND METHOD FOR PERFORMING CUNEIFORM OSTEOTOMY".
According to that technique, and through the use of a saw-guide jig, two cuts are performed to remove a defined-angle wedge from the upper portion of a tibia. This cut wedge is removed, and the remaining tibial portions are rotated relative to one another and fixed in any suitable manner against further relative movement
The method of the present invention proposes an improvement of that technique in the form of a great simplification.
A principal object of the invention is, therefore, to provide such a simplified osteotomy technique which offers a number of important procedural advantages.
According to a preferred method of practicing the invention, a curvilinear cut, and preferably a cut which is substantially cylindrical, is made in the proximal tibia about an axis which is substantially normal to the sagittal plane. This cut frees a caudal, tibial portion within the metaphyseal region from the remaining portion of the tibia that includes the diaphysis and the tibial crest. The thus-cut tibial portions are then rotated relative to one another by the desired corrective angle, without any translation (lateral offsetting) occurring between the metaphysis and the diaphysis, and fixed in any suitable manner against further relative movement, as by means of pins.
Among the important advantages offered by this technique are that (a) only a single cut in the tibia need be made during a surgical procedure, and that (b) this single cut allows infinitely adjustable relative rotation between the cut tibial portions to achieve any desired corrective angle, and that (c) the metaphyseal bone is better for healing.
These and other advantages and features of the invention will become more fully apparent when the description of the same below is read in conjunction with the accompanying drawings.